JotForm is a free online form builder which helps you create online forms without writing a single line of code. No sign-up required.
We believe that if one user has a question, there could be more users who may have the same question. This is why many of our support forum threads are public and available to be searched and viewed. If you’d like help immediately, feel free to search for a similar question, or submit your question or concern.
You might consider the following solution:
1) Disable the Time option on your DateTime field, and add a separate Time field instead.
2) Add a Text warning message.
3) Setup a show condition to show the warning message and hide the form submit button for Time after 10pm.
If you need any further assistance, please let us know.